* Commit 76c2ff3e broke backlight on Chromebook snow
@ 2021-10-21 14:47 Guillaume GARDET
2021-10-22 11:38 ` Dario Binacchi
0 siblings, 1 reply; 6+ messages in thread
From: Guillaume GARDET @ 2021-10-21 14:47 UTC (permalink / raw)
To: Dario Binacchi; +Cc: Simon Glass, Matthias Brugger, u-boot, Akshay Saraswat
Hi,
Commit 76c2ff3e [0] broke backlight on Chromebook snow.
A revert on top of 2021.10 restores the backlight.
Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
Cheers,
Guillaume
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Commit 76c2ff3e broke backlight on Chromebook snow
2021-10-21 14:47 Commit 76c2ff3e broke backlight on Chromebook snow Guillaume GARDET
@ 2021-10-22 11:38 ` Dario Binacchi
2021-10-22 12:34 ` Re : " Guillaume GARDET
2021-11-03 22:50 ` Simon Glass
0 siblings, 2 replies; 6+ messages in thread
From: Dario Binacchi @ 2021-10-22 11:38 UTC (permalink / raw)
To: Guillaume GARDET; +Cc: Simon Glass, Matthias Brugger, u-boot, Akshay Saraswat
Hi Guillaume,
> Il 21/10/2021 16:47 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
>
>
> Hi,
>
> Commit 76c2ff3e [0] broke backlight on Chromebook snow.
> A revert on top of 2021.10 restores the backlight.
> Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
Is it possible that max_level is equal to min_level and therefore division
by zero is done?
Thanks and regards,
Dario
>
> Cheers,
> Guillaume
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
2021-10-22 11:38 ` Dario Binacchi
@ 2021-10-22 12:34 ` Guillaume GARDET
2021-10-23 9:23 ` Dario Binacchi
2021-11-03 22:50 ` Simon Glass
1 sibling, 1 reply; 6+ messages in thread
From: Guillaume GARDET @ 2021-10-22 12:34 UTC (permalink / raw)
To: Dario Binacchi; +Cc: Simon Glass, Matthias Brugger, u-boot, Akshay Saraswat
Hi Dario,
----- Dario Binacchi <dariobin@libero.it> a écrit :
> Hi Guillaume,
>
> > Il 21/10/2021 16:47 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
> >
> >
> > Hi,
> >
> > Commit 76c2ff3e [0] broke backlight on Chromebook snow.
> > A revert on top of 2021.10 restores the backlight.
> > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
>
> Is it possible that max_level is equal to min_level and therefore division
> by zero is done?
I do not think so, because u-boot does not crash and the DTS file has multiple levels:
https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243
I think the problem occurs when 'cur_level == max_level', which is also the default value in the DTS.
If I change the default-brightness-level to 6 (instead of 7), then the backlight works again, which would confirm the assumption above.
pwm_backlight_set_brightness seems to set cur_level to max value by default. Maybe the driver thinks there is nothing to do, since current level is also the desired level?
Cheers,
Guillaume
>
> Thanks and regards,
> Dario
> >
> > Cheers,
> > Guillaume
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
2021-10-22 12:34 ` Re : " Guillaume GARDET
@ 2021-10-23 9:23 ` Dario Binacchi
2021-11-03 22:50 ` Simon Glass
0 siblings, 1 reply; 6+ messages in thread
From: Dario Binacchi @ 2021-10-23 9:23 UTC (permalink / raw)
To: Guillaume GARDET; +Cc: Simon Glass, Matthias Brugger, u-boot, Akshay Saraswat
Hi Guillaume,
> Il 22/10/2021 14:34 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
>
>
> Hi Dario,
>
> ----- Dario Binacchi <dariobin@libero.it> a écrit :
> > Hi Guillaume,
> >
> > > Il 21/10/2021 16:47 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
> > >
> > >
> > > Hi,
> > >
> > > Commit 76c2ff3e [0] broke backlight on Chromebook snow.
> > > A revert on top of 2021.10 restores the backlight.
> > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
> >
> > Is it possible that max_level is equal to min_level and therefore division
> > by zero is done?
>
> I do not think so, because u-boot does not crash and the DTS file has multiple levels:
> https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243
>
> I think the problem occurs when 'cur_level == max_level', which is also the default value in the DTS.
> If I change the default-brightness-level to 6 (instead of 7), then the backlight works again, which would confirm the assumption above.
I have set the default-brightness-level to max-level on my beaglebone board but the backlight works the same.
I didn't see any difference.
Thanks and regards
Dario
> pwm_backlight_set_brightness seems to set cur_level to max value by default. Maybe the driver thinks there is nothing to do, since current level is also the desired level?
>
>
> Cheers,
> Guillaume
>
>
> >
> > Thanks and regards,
> > Dario
> > >
> > > Cheers,
> > > Guillaume
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Commit 76c2ff3e broke backlight on Chromebook snow
2021-10-22 11:38 ` Dario Binacchi
2021-10-22 12:34 ` Re : " Guillaume GARDET
@ 2021-11-03 22:50 ` Simon Glass
1 sibling, 0 replies; 6+ messages in thread
From: Simon Glass @ 2021-11-03 22:50 UTC (permalink / raw)
To: Dario Binacchi
Cc: Guillaume GARDET, Matthias Brugger, u-boot, Akshay Saraswat
Hi,
On Fri, 22 Oct 2021 at 05:38, Dario Binacchi <dariobin@libero.it> wrote:
>
> Hi Guillaume,
>
> > Il 21/10/2021 16:47 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
> >
> >
> > Hi,
> >
> > Commit 76c2ff3e [0] broke backlight on Chromebook snow.
> > A revert on top of 2021.10 restores the backlight.
> > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
>
> Is it possible that max_level is equal to min_level and therefore division
> by zero is done?'
I got this running in my lab now and sent a possible fix.
Regards,
Simon
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
2021-10-23 9:23 ` Dario Binacchi
@ 2021-11-03 22:50 ` Simon Glass
0 siblings, 0 replies; 6+ messages in thread
From: Simon Glass @ 2021-11-03 22:50 UTC (permalink / raw)
To: Dario Binacchi
Cc: Guillaume GARDET, Matthias Brugger, u-boot, Akshay Saraswat
Hi,
On Sat, 23 Oct 2021 at 03:23, Dario Binacchi <dariobin@libero.it> wrote:
>
> Hi Guillaume,
>
> > Il 22/10/2021 14:34 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
> >
> >
> > Hi Dario,
> >
> > ----- Dario Binacchi <dariobin@libero.it> a écrit :
> > > Hi Guillaume,
> > >
> > > > Il 21/10/2021 16:47 Guillaume GARDET <guillaume.gardet@free.fr> ha scritto:
> > > >
> > > >
> > > > Hi,
> > > >
> > > > Commit 76c2ff3e [0] broke backlight on Chromebook snow.
> > > > A revert on top of 2021.10 restores the backlight.
> > > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this?
> > >
> > > Is it possible that max_level is equal to min_level and therefore division
> > > by zero is done?
> >
> > I do not think so, because u-boot does not crash and the DTS file has multiple levels:
> > https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243
> >
> > I think the problem occurs when 'cur_level == max_level', which is also the default value in the DTS.
> > If I change the default-brightness-level to 6 (instead of 7), then the backlight works again, which would confirm the assumption above.
>
> I have set the default-brightness-level to max-level on my beaglebone board but the backlight works the same.
> I didn't see any difference.
I got this running in my lab now and sent a possible fix.
Regards,
Simon
>
> Thanks and regards
> Dario
>
> > pwm_backlight_set_brightness seems to set cur_level to max value by default. Maybe the driver thinks there is nothing to do, since current level is also the desired level?
[..]
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-11-03 22:51 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-21 14:47 Commit 76c2ff3e broke backlight on Chromebook snow Guillaume GARDET
2021-10-22 11:38 ` Dario Binacchi
2021-10-22 12:34 ` Re : " Guillaume GARDET
2021-10-23 9:23 ` Dario Binacchi
2021-11-03 22:50 ` Simon Glass
2021-11-03 22:50 ` Simon Glass
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